1. Field of the Invention
The present invention relates generally to the field of surgery, and more specifically to managing pressure within the eye by controlling the inflow of fluid using a specialized cassette during ophthalmic procedures such as the removal of a cataract.
2. Description of the Related Art
Phacoemulsification surgery has been successfully employed in the treatment of certain ocular problems, such as cataract surgery, including removal of a cataract-damaged lens and implanting an artificial intraocular lens. Phacoemulsification surgery typically involves removal of the cataract-damaged lens and may utilize a small incision at the edge of the cornea. Through the small incision, the surgeon then creates an opening in the capsule, i.e. membrane that encapsulates the lens.
Next, the surgeon may insert an ultrasonic probe, incorporated within the phacoemulsification handpiece, through the opening in the cornea and capsule accessing the damaged lens. The handpiece's ultrasonic actuated tip emulsifies the damaged lens sufficient to be evacuated by the handpiece. After the damaged natural lens is completely removed, the handpiece tip is withdrawn from the eye. The surgeon may now implant an intraocular lens into the space made available in the capsule.
While performing phacoemulsification surgical techniques, such as lens removal, it is necessary for the surgeon to be able to stop the flow of fluid into the phaco handpiece tip and into the ocular cavity. Stopping the flow generally entails reversing the flow of fluid, such as by reversing pump operation. One example of a need to stop flow is encountering an occlusion during emulsification of the damaged lens, wherein the tip of the phaco handpiece may become partially blocked or occluded. As the tip becomes further blocked or completely occluded, the vacuum in the aspiration line of the phaco handpiece builds proportionally. When the tip becomes unoccluded, due to removal or movement of the occlusion, the handpiece begins aspirating fluid to equalize the resulting pressure differential between the eye and the aspiration line. In order to stop the flow, the aspiration line can be vented to ambient pressure, the pump can be stopped, a pressure source can be reversed, such as a reversible peristaltic pump or an irrigation bottle or via an other mechanism known in the art. Flow may be stopped by the concept of reflux. Reflux occurs when pump pressure is reversed, thereby building pressure, and a positive pressure regulator is employed such that fluid flows backward once pressure is released.
When aspirating, venting, and/or refluxing, the present design typically employs two or more pumps. Any pump known in the art may be used with the present invention, including, but not limited to, peristaltic, venturi (wherein fluid flowing through a narrowing pipe produces vacuum as a result of the “Venturi effect”), and/or other flow or vacuum based pumps. In general, designs that operate efficiently in this dual-pump environment, wherein aspiration, venting, reflux, and/or irrigation may be initiated and terminated intermittently, can provide significant benefits in an operating room environment.
Many existing cassettes operate together with a single vacuum source, such as a single type of pump. When the phacoemulsification device has dual pump capability, it typically employs a specific replaceable cassette that enables dual pump operation and can be changed after a surgical procedure. A dual pump cassette exhibiting an efficient venting mechanism that can aspirate or irrigate fluid is highly beneficial.
Providing vacuum from different types of pumps or different types of devices enabling precision aspiration and irrigation can be desirable in an operating room situation. While certain multiple pump type cassettes have previously been offered, reliability in venting, aspirating and operating these cassettes can at times be imperfect, particularly in precise operating environments. Further, certain existing designs simply transfer all fluids into a reservoir, thereby rapidly filling up the reservoir, which is undesirable. If the reservoir is filled too rapidly or too frequently during a procedure, valuable time can be lost while the reservoir is drained. Additionally, previous designs have offered arrangements wherein both venting and aspiration are performed in a single line, such as a line connected to the reservoir. Separation of venting and aspiration functions can be advantageous and can provide improved performance over a single line used to perform both functions.
Also, certain previous designs include vent valves or other mechanisms which are sometimes undesirable. It would be beneficial to offer a dual pump cassette that employs minimal components or components that efficiently perform the aspiration and irrigation tasks required in the ocular surgical environment.